I am dead scared of diving with sperm whales because they can do to you what a submarine does when it launches a ping (aka vibrate your body with 265 dB clicks till you turn into mush). They could kill an entire diving party before it could even see them. The line between a wondrous experience and an atrocious death is drawn by the whim of an animal no smarter than a dog, and this frightens me immensely.